1. Field of the Invention
The present invention relates to an electroluminescent element. More particularly, it is concerned with an electroluminescent element in which the luminescent material is an organic compound.
2. Description of the Prior Art
Prior art electroluminescent elements have two or three layers of organic compounds. For example, the one shown in FIG. 1 has an organic fluorescent substance thin film 3 and an organic hole transport layer 4 laminated on top of the other, which are sandwiched between a metal electrode 1 as a cathode and a transparent electrode 2 as an anode. The one shown in FIG. 2 has an organic electron transport layer 5, an organic fluorescent substance thin film 3, and an organic hole transport layer 4 laminated on top of the other, which are sandwiched between a metal electrode I and a transparent electrode 2. The organic hole transport layer 4 facilitates the injection of holes from the anode and blocks electrons, and the organic electron transport layer 5 facilitates the injection of electrons from the cathode. The transparent electrode 2 is provided with a glass substrate 6. The metal electrode 1 injects electrons and the transparent electrode 2 injects holes, and the recombination of the electrons and holes generates excitons, which emit light as they are deactivated through radiation. This light radiates outward through the electrode 2 and the glass substrate 6.
The conventional electroluminescent element having the organic fluorescent substance thin film 3 constructed as indicated above has a disadvantage in that it emits light of limited spectra, for example, green light having a wavelength of about 530 nm, and it does not emit blue light of high purity at a high luminance.